Low-temperature tough ferrite nodular cast iron of 60 DEG C below zero and preparation method thereof

Abstract

The invention provides a low-temperature tough ferrite nodular cast iron of 60 DEG C below zero and a preparation method thereof. The low-temperature tough ferrite nodular cast iron of 60 DEG C below zero comprises the following components in percentage by weight: 3.60-3.80 percent of C, 1.80-2.1 percent of Si, less than 0.08 percent of Mn, less than 0.025 percent of P, less than 0.01 percent of S, less than 0.02 percent of Ti, 0.3-0.7 percent of Ni, 0.03-0.05 percent of Mg residue, less than 0.01 percent of Re residue and the balance of Fe. The preparation method of the low-temperature tough ferrite nodular cast iron of 60 DEG C below zero comprises the following steps: 1, smelting, spheroidizing and inoculating pig iron, waste steel and spheroidized alloy in sequence; 2, pouring molten iron into a cavity from a spheroidizing bag, wherein the pouring temperature is 1,440-1,380 DEG C within 6 minutes from the end time of the spheroidizing treatment to the pouring end time; 3, performing annealing heat treatment on the low-temperature ductile iron of cast iron. The low-temperature ductile iron meanwhile has good toughness at the temperature of 60 DEG C below zero under the condition that high strength is kept, and the standard requirements corresponding to QT400-18AL are met.

Description

technical field [0001] The invention relates to a ferritic nodular cast iron, in particular to a low-temperature ferritic nodular cast iron. Background technique [0002] With the expansion of high-speed train operation to lower temperature areas, QT400-18AL low-temperature ductile iron with ultra-low temperature, high strength (≥400MPa), and high toughness (≥12J) at -50°C and -60°C has been proposed. [0003] Since the tensile strength and impact performance of ductile iron have a strong mutual restriction relationship, a large number of tests and production data show that, as far as the existing production process is concerned, when the temperature drops to -50 ° C, the degree of restriction is close to QT400 The "limit" of the -18AL technical standard. Table 1 is the inspection result of the secondary sample of low-temperature ductile iron provided for the patent CN102120253A of our company. [0004] If the ratio of the drop value of impact energy in different temperatu...

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Problems solved by technology

[0010] The technical problem to be solved by the present invention is: to overcome the deficiency that low-temperature ductile iron in the prior art cannot maintain good toughness at ultra-low temperatures of -60°C under the condition of maintaining high strength (400MPa), and to provide -60°C low-temperature ductile ferrite Spherical ductile iron and preparation method thereof

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